Studies on Synthesis, Characterization and Applications of Microencapsulation Process Via Interfacial Polymerization

SYNOPSIS OF THE THESIS ENTITLED

Studies on Synthesis, Characterization and Applications of Microencapsulation Process via Interfacial Polymerization

Submitted to

GUJARAT TECHNOLOGICAL UNIVERSITY, AHMEDABAD

For the Partial fulfilment of the Degree Of

Doctor of Philosophy

CHEMICAL ENGINEERING

Submitted BY

Christian Ujvala Parsottamdas (Enrolment Number: 129990905004)

Research Supervisor: Dr. Shrikant J. Wagh

Principal, SHROFF S. R. ROTARY INSTITUTE OF CHEMICAL TECHNOLOGY

Doctoral Progress Committee (DPC) Members

Late Dr. Suhas A. Puranik Dr. Sachin Parikh Ex. Director, Environmental Cell, Professor in Chemical Engineering Atmiya University, Rajkot. Joint Director, DTE- Gandhinagar. CONTENT

Sr. Title Page No. No.

1. Title of thesis and Abstract 3-4 2. Brief description on the state of the art of the research topic 4-6 3. Definition of the problem 6-7 4. Objective and Scope of work 7 5. Original contribution by the thesis 7-8 6. Methodology of research, Result/Comparisons 8-13 7. Achievements with respect to objectives 13-14 8. Conclusions 14 Copies of papers published and a list of all publications arising 9. 15 from the thesis 10. References 16

2 1. Title of thesis and Abstract

Title of thesis: Studies on Synthesis, Characterization and Applications of Microencapsulation Process via Interfacial Polymerization

Abstract:

Microencapsulation is the technology of packaging of micronized solid particles, liquid droplets, or gas bubbles in microcapsules by applying thin film of coating or shell material. Resulting microcapsules are particles with diameters between 1µm to 1000µm.They have a core/shell structure which contains polymeric material as a wall (shell) enclosing the core. Synthesis of microcapsules is considered as microencapsulation process which can be categorized into two groups: (i) chemical processes like In-situ polymerization, Interfacial polycondensation, Interfacial cross- linking, matrix polymerization etc. and (ii) physical processes like spray–drying, pan coating, centrifugal extrusion, air-suspension coating etc. In this work, the generic Interfacial polymerization process is considered as Interfacial polycondensation (IP) that is step-growth polymerization reactions taking place at the interface.

Interfacial polycondensation (IP), through several step-growth reactions, opens a wide window for synthesis of microcapsules (and membranes also) at ambient conditions without stringent conditions of monomer purity. IP is one of the important methods for synthesis of microcapsules. It offers advantages over other methods because it involves a chemical reaction between monomers dissolved in two different immiscible solvents. Variables such as nature of solvent, reactivity of monomers, types and concentration of surfactant, rate of chemical reaction, reaction conditions etc. play a vital role in deciding the characteristics of microcapsules produced. These give a great leverage over achieving the properties of microcapsules for certain pre decided applications, which may include encapsulation of pharmaceuticals, food additives, agrochemicals, solvents, adhesives, immobilization of living cells etc.

The research work presented includes study of various aspects of microencapsulation via IP to form polymer shell, and release behaviour of certain encapsulated agrochemicals as active ingredients through polymer shell. The experimentation includes systematic study on synthesis of polyurea microcapsules under specific preparative conditions controlling the kinetic and mass transfer regimes of reaction to produce polyurea microcapsules as a tailor made product. Synthesis experimentation is 3 necessarily followed by characterization of the product formed. Various analytical tools like Fourier Transform Infrared (FTIR) Spectrophotometer, Differential Scanning Calorimeter (DSC), Scanning Electron Microscope (SEM), and X-ray Diffractometer (XRD) are used to characterize polymeric shell of microcapsules for its application of controlled/sustained release.

2. Brief description on the state of the art of the research topic:

Interfacial polycondensation (IP) involves a chemical reaction between monomers dissolved in two different immiscible solvents [1]. Step growth polymerization reactions occur at, or in a thin region adjacent to the interface of the two immiscible phases, and since the polymer formed is insoluble in both the phases, accumulate at the surface of contact between the phases as shown in Figure-1[2]. IP is a heterogeneous process of mass transfer with chemical reaction and simultaneous occurrence of polymer phase separation and ﬁlm formation [3]. The steady state concentration profiles of the monomers (Hexamethylene diamine and Hexamethylene di-isocyanate) used in a typical polycondensation reaction with concurrent phase separation of polyurea formed are shown schematically in Figure-1.

Figure 1 Schematic diagram showing different regions of Interfacial Polycondensation 4 Where, A0a= unprotonated diamine concentration in bulk aqueous phase, A0ap= diamine concentration at aqueous phase-polymer interface, A0r= diamine concentration in reaction zone, AT = total diamine concentration in bulk aqueous phase, B0r= diisocyanate concentration in the reaction zone, B0s= diisocyanate concentration in the bulk organic phase, = partition coefficient of diamine between aqueous phase and polymer film and = partition coefficient of diamine between polymer film and organic solvent.[4,5] Interfacial polycondensation (IP) is one of the most widely used chemical processes for microencapsulation of agrochemicals as active ingredients for effective release to the target [6, 7]. As it happens with any product produced via a chemical reaction or a set of chemical reactions that the properties are determined by the reaction conditions and process variables, the synthesis of microcapsules loaded with active ingredient (AI) via IP is also governed by several physico-chemical factors and variables enlisted above in the abstract. The encapsulation of AI is mainly done for controlled/sustained release of AI, insecticides in this work, to obtain certain formulation. Thus it is a formulation technique that can offer multiple advantages stated below:

 Reduction of toxic effects.  Enhancement of the duration of activity for an equal level of insecticide.  Overall reduction in total consumption of insecticide.  Reduction in evaporative losses.  Protection of/from the external environment, and increase in use and handling convenience [8-11].

It is known from earlier works that polyurea synthesized by IP offers good flexibility in desirable properties of microcapsules for required release rates of active ingredient (AI) [12-13]. Various researchers have studied different operating parameters e.g. reactivity of monomers, types and concentration of surfactant, speed of agitation, different reaction parameters on reaction kinetics of synthesis of polyurea membrane by IP through experimental and modelling studies correlating rate of reaction with polymer film properties like film thickness, crystallinity and molecular weight distribution (MWD) [14-16].

5 Study of the reported literature makes it clear that the IP reaction for synthesis of polyurea can be effectively used to make a polymer shell to encapsulate different core materials in it for controlled/sustained release. Several process conditions, such as monomer concentration ratio, phase volume ratio and number of moles of limiting monomer, and intrinsic properties like polarity of organic solvents and partition coefficient of aqueous phase monomer have significant effect on product properties. The available literature on polyurea synthesis via IP shows that sufficient experimental work is still required to prove legitimate claim of IP for making tailor-made polyurea microcapsules as a formulation for insecticides. The present work tries to address these issues and provides deeper insights. Study on effect of temperature on kinetics of IP and effect of a pendant group in solvent structure discussed in this work have not been covered by earlier workers. Experimental process followed and the variables studied in this work for the kinetic study (such as, bulk mole ratios of the monomers, R, the number of moles of limiting monomer per unit volume of dispersed phase, nL/Vd, and phase volume ratio, Vd/ Vc) are the integral part of the work as have been considered by earlier researchers. But, for experimental validation and corroboration purpose their values have been kept in similar range. However, a wide range of values has been studied to enable us to make certain conclusive remarks on microcapsules as a final product. Polyurea microcapsules were characterized by FTIR, XRD, DSC and SEM.

After synthesis, towards application part of the work, release trends of three selected insecticides i.e. chlorpyriphos, cypermethrin (pesticides) and pretilachlor (herbicide) as a core material in polyurea shell were also studied. Encapsulation efficiency was calculated and rates of release of these insecticides into methanol was measured experimentally in controlled release experiments and reported. Semi crystalline polyurea shell material was synthesized and polymer crystallinity correlated with experimental variables and final applications i.e. encapsulation efficiency and release rate of insecticides.

3. Definition of the Problem: The present doctoral work entails the following studies: [1] To synthesize polyurea microcapsules via IP to study effect of different experimental variables like monomer mole ratio (R), number of moles of limiting monomer per unit

volume of dispersed phase (nL/Vd), phase volume ratio (Vd/Vc) and reaction temperature (T) on properties of polymer produced.

6 [2] To study the effect of various organic solvents and temperature of reaction on properties of polyurea microcapsules via IP. [3] To encapsulate three different insecticides i.e. chlorpyriphos, cypermethrin and pretilachlor in synthesized polyurea shell and calculate % encapsulation efficiency. [4] To study release rate of three different insecticides i.e. chlorpyriphos, cypermethrin and pretilachlor encapsulated in polyurea shell into release media (methanol) and correlate encapsulation efficiency and release rates with % crystallinity and experimental variables like monomer mole ratio (R), number of moles of limiting

monomer per unit volume of dispersed phase (nL/Vd) in order to make a tailor made formulation.

In this research work, systematic study of each of above aspects was carried out via experimental investigations to suggest the solution.

4. Objective and Scope of work: 4.1 Objectives: 1. Experimental studies on synthesis and characterization of polyurea microcapsules via IP at specific preparative conditions.

2. Study the effect of different solvents on reaction kinetics of IP at different temperatures.

3. Encapsulation of selected insecticides (i.e. active ingredients (AI)) in polyurea shell to study their controlled release behaviour via experiments.

4. Correlate encapsulation efficiency and release rate of active ingredient (AI) with morphological parameters of microcapsules as well as process variables.

4.2 Scope of Work:

The present research work is mainly an experimental work on synthesis of polyurea microcapsules via IP at different preparative conditions and reaction temperature which addresses each of the above objectives. Polyurea shell was characterized using various analytical tools like Fourier transform infrared (FTIR) spectrophotometer, powder XRD analysis, Differential scanning calorimeter (DSC) and scanning electron microscope (SEM). IP reaction rate was studied using different organic solvents: (i) Cyclohexane (ii) n-Octane (iii) Benzene (iv) Toluene (v) p-Xylene and (vi) Mesitylene. Three different insecticides i.e. chlorpyriphos, cypermethrin and pretilachlor were encapsulated in

polyurea shell via IP at different preparative condition i.e. R=1.2, 2.4 and nL/Vd= 0.36,

7 0.72. Encapsulation efficiency was calculated and a rate of release of these insecticides into methanol was measured experimentally in controlled release experiments, and correlated with % crystallinity of polyurea.

5. Original contribution by the thesis: Among the various objectives of microencapsulation, controlled release of an active ingredient is perhaps the most engaging and challenging. IP is one of the most effective techniques for the synthesis of microcapsules loaded with an active ingredient. The present work tries to examine effect of different reaction parameters on reaction kinetics of polyurea synthesis via IP which governs other process variables resulting into change in % crystallinity of polyurea shell. Three different insecticides were successfully encapsulated in polyurea shell as an active ingredient and its controlled release data were correlated with % crystallinity. This study will be useful to get tailor made microcapsules encapsulated with insecticides in order to get its sustained or delayed release from polyurea shell.

6. Methodology of research, Result/Comparisons: 6.1. Synthesis of Polyurea Microcapsules:

The polyurea microcapsules were synthesized according to the procedure reported in the literature [12-13]. A two-step procedure was adopted, and the total volume of the aqueous phase was constant in all experiments. In the first step, oil-in-water emulsion (oil: water = 1:2 v/v) was prepared by dispersing the organic phase; a solution of a desired concentration of HMDI in solvent n-Octane-in distilled water, with Tween-85 (4% v/v, of the distilled water) as the emulsifying agent. The emulsification of the organic phase and aqueous phase was carried out using a mechanical stirrer with a shrouded, four-bladed, pitched turbine impeller, stirring at 3000 ± 20 rpm for 15 min. This step was identically performed in all of the experiments to obtain the same drop size distribution of emulsion and particle size of microcapsules, as reported in the literature.

In the second step, an appropriate volume of this emulsion (Vd/Vc = 0.05) was added to an aqueous solution of HMDA, and the reaction mixture was continuously stirred at 200 rpm. Interfacial polycondensation was carried out between HMDI in the dispersed phase (present in the emulsion) and HMDA in the aqueous phase. The reaction temperature was continuously monitored and controlled with a temperature probe attached to a data acquisition system. The progress of the reaction was monitored by measuring the change in pH of the reaction mixture with the use of an advanced Programmable Logical 8 Controller based pH Logger equipped with high responsive pH probe until it reached a constant value. Polyurea microcapsules were filtered, washed with n-Octane, dried under vacuum, and stored in a moisture-free environment. Three different experimental parameters (i) initial monomer mole ratio (R) i.e. 0.6, 1.2 and 2.4 (ii) number of moles of 3 limiting monomer per unit volume of the dispersed phase ( nL/Vd, kmol/m ) ) i.e. 0.18, 0.36 and 0.72 and (iii) reaction temperature, T = 20°C, 25°C and 30°C were employed to study its effect on kinetics. To study the effect of pendant group of organic solvent on reaction kinetics of polyurea microcapsules synthesized via IP, four different organic solvents Benzene, Toluene, p-Xylene and 1,3,5- Trimethyl benzene (mesitylene) were selected.

6.2. Synthesis of Insecticide-loaded Polyurea Microcapsules:

Chlorpyriphos, cypermethrin and pretilachlor were selected as an active ingredient (AI) for encapsulation in the IP synthesized polyurea shell as shown in Fig. 2.

Aqueous Phase: [Water + 4% (w/v) Tween- Continuous Phase: [Water + HMDA] 85]

Step-I: Emulsion Step-II: Interfacial (o/w) Preparation Polycondensation Reaction (stirring at 3000RPM (continuous stirring of the reaction for 15 minutes) mixture at 200 RPM)

Organic Phase: Filtration and Washing of Polyurea [n- Octane +HMDI microcapsules with distilled water +Insecticide]

1 gm of Microcapsules in 100 ml of methanol to study controlled release Figure 2 Steps in the synthesis of polyurea microcapsules containing insecticide as a core material via IP.

9 6.3. Release Rate Measurement:

Polyurea microcapsules containing insecticide sample (as an active ingredient and core material) with constant loading content of 4% (w/v) were filtered, washed with distilled water, and lightly blotted to remove excess surface moisture. One gram of these microcapsules was added into the release cell containing 100 ml methanol and kept in a sonicated bath at 28°C. At regular intervals, 10 ml of sample was withdrawn using a syringe, filtered with filter paper, and its absorbance recorded using a pre-calibrated UV- spectrophotometer (UV-1800, UV-VIS Shimadzu, Japan). Fresh methanol was added to the cell to maintain a constant volume of the continuous phase. Following the methods of Takashi et al., and Scopean et al., encapsulation efficiency and percent release of insecticide were determined [ 17-18].

% Encapsulation = × 100

, % Release of Insecticide = × 100 6.4. Characterization:

Polyurea microcapsules were characterized by Fourier transform infrared (FTIR) spectrophotometer (Spectrum One, Perkin Elmer), powder X-ray diffractometer (Model D2 Phaser, Bruker, USA ), scanning electron microscope (FEG SEM, Phillips) and TGA/DSC-1 METLER TOLEDO between 30°C and 500°C with a heating rate of 10°C/min.

6.5 Results: 6.5.1 Reaction kinetics for synthesis of polyurea microcapsules via IP: IP reaction was carried out as discussed in 6.1, for synthesis of polyurea microcapsules at ambient condition of temperature and pressure using Cyclohexane, n-Octane as different organic solvents. Three different values for monomer mole ratio, R i.e. 0.6, 1.2 and 2.4 and three different values of number of moles of limiting monomer per unit volume of the dispersed phase, nL/Vd, i.e. 0.18, 0.36 and 0.72 were applied in these experiments for constant value of phase volume ratio i.e. 0.05. Kinetic data for the progress of the reaction was monitored by measuring the change of pH of the reaction mixture (i.e. decrease in concentration of HMDA in aqueous phase) and plotted against reaction time. Several such plots are made. One sample plot for polurea synthesis by IP with n-Octane as a solvent is shown in Fig. 3.

10 Figure 3 Rate of IP reaction for monomer mole ratio, R=2.4 (other conditions: nL/Vd =0.72,

T=25°C, Vd/Vc=0.05)

Polyurea formed under condition of R=0.6 and nL/Vd = 0.18 is of less yield since R<1, HMDI is a limiting monomer and the reaction occurs on the organic side of the interface leaves HMDA unreacted. These preparative conditions were omitted from rest of experimental work. Three different phase volume ratios i.e. 0.05, 1 and 2 were experimentally checked for Cyclohexane, n-Octane as a solvent and other experimental parameters were constant. It was observed that reaction rate increased with increase in phase volume ratio. Phase volume ratio is an important variable governing one of the process parameters of IP i.e. interfacial area.

6.5.2 Effect of reaction temperature:

Reaction temperature is an important process variable and to our knowledge, no experimental data are available on the effect of temperature on polyurea synthesis via IP reaction. Therefore, experimental kinetic data are reported for three different reaction temperatures i.e. 20°C, 25°C and 30°C to study effect of reaction temperature on polyurea synthesis by IP. In our experiments, as expected, it was observed (Fig. 4) that the reaction is faster at 35°C compared to that at other two temperatures (25 °C and 20°C). Increase in reaction temperature promotes transfer of HMDA from aqueous phase to organic phase by increasing its diffusion coefficient and its partition coefficient results into increase in reaction rate.

11 Figure 4 The effect of temperature on rate of IP reaction (other conditions: R = 2.4, nL/Vd = 0.36,

Vd/Vc = 0.05, Solvent n-Octane).

6.5.3 Effect of different organic solvents: One of the objectives of the current research work is to study the effect of different organic solvents (for organic phase monomer, HMDI) on reaction kinetics. Four different organic solvents, (i) Benzene (ii) Toluene (iii) p-Xylene and (iv) Mesitylene with incremental order of methyl pendant group were selected and experimental kinetic data plotted as shown in Fig. 5. Dielectric constants for selected organic solvents reported in literature are: Toluene (2.39) > p-Xylene (2.30) > Benzene (2.28) > Mesitylene(2.24) [19- 20]. Polarity of solvent is directly related with its dielectric constant. It was observed that reaction rate decreases with increases in polarity of organic solvent irrespective of number of methyl pendant group associated in molecular structure of organic solvent. It can be therefore, said that solvent polarity with respect to aqueous medium is a more influencing parameter on the rate of reaction than the pendant group in its molecular structure.

Figure 5 The effect of different organic solvents on rate of IP reaction (other conditions: R = 1.2, 0 nL/Vd = 0.72, Vd/Vc = 0.05 and T= 30 C)

12 6.5.3 Results of XRD Analysis:

As shown in Figure 6 a-d, X-ray diffractograms of four different samples of polyurea synthesized suggest a semi crystalline polymer. Percentage crystallinity was calculated using ORIGIN-85 software of these samples (and also of many other samples prepared under various preparative conditions).

Figure 6 XRD patterns for the polyurea shell material: (a) R15; (b) R17; (c) R22; and (d) R24.

6.5.4 Results of Controlled release studies :

Chlorpyriphos, cypermethrin and pretilachlor were encapsulated in the IP synthesized polyurea shell under certain preparative conditions and their release rates into methanol [at 28°C to 30°C] were experimentally measured using UV-Spectrophotometer. A sample plot for controlled release behaviour of cypermethrin encapsulated in polyurea shell is shown in Fig.7. Percentage encapsulation efficiency and release rates were calculated and correlated with experimental variables and percentage crystallinity of polyurea.

Figure 7 Release of encapsulated cypermethrin through polyurea

13 7. Achievements with respect to objectives: Objective Achievement 1. Experimental studies on synthesis Various preparative parameters play important and characterization of polyurea role in governing the reaction rates and hence

microcapsules via IP at specific final properties of polyurea. R=1.2 and nL/Vd preparative conditions. =0.36 found optimum condition for IP reaction rate and polymer crystallinity. 2. To study the effect of different In IP reaction, locus of reaction is on the solvents on reaction kinetics of IP at organic side of the interface, therefore reaction different temperature. rate decreases with increases in polarity of organic solvent irrespective of number of pendant group associated in molecular structure of organic solvent. 3. Encapsulation of selected different Experiments were successfully completed to Insecticides (i.e. active ingredients encapsulate chlorpyriphos, cypermethrin and (AI)) in the synthesized polyurea pretilachlor in the IP synthesized polyurea microcapsules in order to study their shell under certain preparative conditions

controlled release behaviour via (R=1.2, 2.4 and nL/Vd = 0.36, 0.72 and their experiments. release rates into methanol [at 280C to 300C] have been experimentally measured using UV- Spectrophotometer. 4. Correlate encapsulation efficiency and Encapsulation efficiency and release rate were release rate of active ingredient (AI) calculated and correlated with experimental with morphological parameters of parameters and % crystallinity of polyurea microcapsules as well as process shell. A paper based on this experimental work variables. has been submitted to ‘Asian Journal of Chemistry’ and it is under revision.

5. Conclusion On the basis of results, it can be stated that IP is one of the most effective methods which can be used to synthesize polyurea microcapsules. Rate of release and % encapsulation efficiency of insecticides largely depends on structure of polymer formed which is influenced by preperative conditions. Reaction temperature is one of the important conditions which has strong effect on reaction kinetics of polyurea synthesis via IP. In 14 this experimental study increase in reaction temperature promotes transfer of HMDA from aqueous phase to organic phase by increasing its diffusion coefficient and its partition coefficient which accelerates polymer membrane formation. At a low temperature, reaction rate decreases resulting into a more orderly structural molecular arrangement which increases % crystallinity of polyurea. Polarity of organic solvent governs reaction rate of IP, as reaction occurs on the organic phase side of the interface. Reaction rate decreases with increase in solvent polarity irrespective of number of methyl pendant group present in molecular structure of the solvent molecule. Controlled release of encapsulated insecticide largely depends on the properties of semicrystalline polyurea shell. Encapsulation efficiency and release rate of chlorpyriphos, cypermethrin and pretilacholr increases with decrease in R and increase in nL/Vd. Crystallinity of Polyurea has inverse correlation with shell permeability. Increment in % crystallinity reduced diffusive losses of core material through polymeric shell and increase % encapsulation efficiency. The above work provides a pathway based on experimental work to making a tailor made polyurea capsules loaded with insecticides. Also, IP offers a flexible set of parameters to control the final product structure to suit the desired controlled/sustained release behaviour.

9. Copies of papers published and a list of all publications arising from the thesis 9.1 Paper published in an International Journal:

[1]Ujvala P. Christian, Shrikant J. Wagh, ‘Effect of Phase Volume Ratio on Synthesis of Polyurea Microcapsules by Interfacial Polymerization’, International Journal of Advanced Research in Engineering and Technology, Vol. 9, Issue 3, (2018), 60-65. (Scopus Indexed, ISSN: 09766480). [2]Ujvala P. Christian, Shrikant J. Wagh, “Controlled Release of Insecticides through Polyurea Microcapsules Synthesized by Interfacial Polycondensation”, Asian Journal of Chemistry, Vol.30, No. 11(2018), 2571-2576. (Scopus Indexed & UGC Approved Journal No.8774, ISSN: 09707077). [3]Ujvala P. Christian, Shrikant J. Wagh, ‘Experimental Studies on n-Octane and Cyclohexane as Organic Solvent for Synthesis of Polyurea Microcapsules by Interfacial Polycondensation’ Asian Journal of Engineering and Applied Technology, Vol. 9, Issue 3, (2018), 60-65. (ISSN: 09766480).

15 9.2 Paper presented at International Conferences:

[1] Ujvala P. Christian, Shrikant J. Wagh ‘Review of Experimentally Studied Systems for Synthesis of Polymer Microcapsules by Interfacial Polymerization’ was presented in an International Conference ‘CHEMCON-2014’ at Punjab University, Chandigarh during 27th to 30th December-2014. [2] Ujvala P. Christian ‘Synthesis and Characterization of Polyurea Microcapsules derived from Hexamethylene Diamine (HMDA) and Hexamethylene Diisocyanate (HMDI)’ in an International Conference International Conference Women in Science & Technology: Creating Sustainable Career (ICWSTCSC–2016) at BVM- Engineering College, V.V.NAGAR , Gujarat during 28th to 30th January-2016. Published in Indian Journal of Technical Education (IJTE), ISSN: 0971-3034. [3] Ujvala P. Christian, Shrikant J. Wagh ‘Effect of Phase Volume Ratio and Organic Solvent on Polyurea Synthesis by Interfacial Polycondensation’ in an International Conference on "Paradigm shift in Chemical Engineering education, processes and technology" organized by The Institution of Engineers India (IEI)- Gujarat State Centre, at IEI Centre, Ahmedabad-Gujarat during 16th -17th September-2017. [4] Ujvala P. Christian, Shrikant J. Wagh ‘Study on the Effect of Kinetic Parameters on Controlled Release of Chlorpyriphos through Polyurea Shell Synthesis by Interfacial Polycondensation’ in an International Conference GTU-ICON 2019 (Engg. and Tech.), organized by Gujarat Technological University, Ahmedabad-Gujarat on16th March-2019.

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